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CASE REPORT: The case of the unilateral keratoconic conman

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By Rex Wallis
BOptom Hons

 

A fellow eye in a patient also turns out to be keratoconic, with the cone far enough below the visual axis so that it does not interfere with his vision or distort the keratometer mires.

About 15 years ago, 31-year-old GL presented to my practice. He had been diagnosed with unilateral keratoconus about 10 years earlier. He rarely wore his rigid contact lens in his left eye because it was uncomfortable, but the better vision made his eyes feel ‘less strained’ so he wished for an improved contact lens if possible.

Unaided visual acuity was R 6/4.8 L <6/60 with refractive error R plano L not measureable. I had no topographer or pachymeter at the time, but the Bausch and Lomb keratometer mires were not distorted with the RE (7.50@180/7.50@90) and very distorted with the LE (approximately 4.75@180/ 4.50@90). The L central cornea was very thin, appearing to be less than 0.25 corneal thickness compared to the periphery, with central scarring (Figures 1 and 2).

CL OL 26 Rex Wallis Case Study _1 - F

Figure 1

CL OL 26 Rex Wallis Case Study _2 - F
Figure 2

His old contact lens was a proprietary keratoconic design, with back optic zone radius 5.3, but was very flat centrally and very steep in the periphery. Back vertex power was -18.50 and visual acuity with this lens was 6/12= which improved to 6/9.5= with -1.25 over refraction. He was fitted with a new rigid lens, of custom design (KRex 1) from the long-gone NuContacts, with BOZR 4.6 BVP -26.00, which gave visual acuity of 6/9.5= but was comfortable enough to wear and helped his eyes feel ‘more balanced and less strained’.

I spoke to the local corneal specialist about GL’s thin cornea at that time because I was worried about perforation. His response was: ‘The chance of spontaneous rupture is almost zero. Send him in for deep lamella grafting when he cannot wear the contact lens any more.’ That was 15 years ago.

A few years later, the wonders of modern technology—corneal topography—proved that GL was a bit of a con when it came to his unilateral keratoconus.

Despite his RE being 6/4.8 unaided, this eye turned out to also be keratoconic, but evidently the cone was far enough below the visual axis so as not to interfere with his vision or distort the keratometer mires (Figures 3 and 4).

CL OL 26 Rex Wallis Case Study _3 - F
Figure 3

CL OL 26 Rex Wallis Case Study _4 - F
Figure 4

OCT showed the L cornea was thin at around 200 µm but not as thin as the optic section suggested (Figure 5).

CL OL 26 Rex Wallis Case Study _5 - F
Figure 5

GL’s condition remains stable so life for our hero goes on without drama—without unilateral keratoconus or perforation, despite deceiving initial appearances.

____________________

I thank Gavin O’Callaghan for the images.



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